[Cast] In Audio/VideoSender, drop frames when too-long a duration is in-flight.

media/cast/sender/rtp_timestamp_helper.cc

-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-#include "media/cast/sender/rtp_timestamp_helper.h"
-
-namespace media {
-namespace cast {
-
-RtpTimestampHelper::RtpTimestampHelper(int frequency)
-    : frequency_(frequency),
-      last_rtp_timestamp_(0) {
-}
-
-RtpTimestampHelper::~RtpTimestampHelper() {
-}
-
-bool RtpTimestampHelper::GetCurrentTimeAsRtpTimestamp(
-    const base::TimeTicks& now, uint32* rtp_timestamp) const {
-  if (last_capture_time_.is_null())
-    return false;
-  const base::TimeDelta elapsed_time = now - last_capture_time_;
-  const int64 rtp_delta =
-      elapsed_time * frequency_ / base::TimeDelta::FromSeconds(1);
-  *rtp_timestamp = last_rtp_timestamp_ + static_cast<uint32>(rtp_delta);
-  return true;
-}
-
-void RtpTimestampHelper::StoreLatestTime(
-    base::TimeTicks capture_time, uint32 rtp_timestamp) {
-  last_capture_time_ = capture_time;
-  last_rtp_timestamp_ = rtp_timestamp;
-}
-
-}  // namespace cast
-}  // namespace media